1. Field of the Invention
This invention relates generally to an infrared detector, and more particularly, to an infrared detector which separates current induced by gamma ray radiation from current induced by infrared radiation.
2. Discussion of the Related Art
Infrared detectors for detecting infrared radiation typically to monitor temperature or temperature gradients are known in the art. There exists a wide range of different applications, however, in which one would want to utilize an infrared detector. These applications range from generating a night time image to infrared spectroscopy. Some of these applications require infrared detection from a remote location in a radiation environment such as may be encountered in space and performed upon certain satellites. Other infrared detection application in radiation environments are also known.
Typically an infrared detector will be an electrical device which will respond to incident infrared radiation. One problem in any type of electrical detector is the minimum threshold of observable incident energy ascertainable because of the existence of electrical noise. For an infrared detector, the incident infrared radiation must generate enough energy within the detecting material to raise the detectable energy level above the system noise level. In most designs, the infrared detector will be cooled to a very low temperature to reduce the interference caused by electrical noise.
Other factors may add to the degradation of the minimum threshold of observable energy. In a radiation environment, the amount of interfering radiation as a result of gamma rays presents a significant problem in infrared detectors since the gamma rays are at a high energy level, and thus, the gamma rays add significantly to the noise of the infrared detecting device. It is therefore necessary that the gamma ray interference be kept below the system noise level.
The most popular infrared detectors include a semiconductor semiconductor appropriately configured such that an interacting infrared photon will create charge carriers by giving up energy to bound electrons within the semiconductor material. If a bias voltage is applied to the semiconductor material the charge carriers will add to the current which can then be measured to observe increases in current indicating photon interaction. Since a gamma photon will have more energy than an infrared photon, it is more apt to generate more and higher energy charge carriers creating greater current in the semiconductor material. Consequently, the amount of current within the semiconductor device caused by the gamma radiation raises the current above the system noise level of the device such that the current caused by the infrared radiation is obscured. Different methods are known in the art for reducing the current in an infrared semiconductor detector caused by incident gamma radiation, such as providing undoped blocking layers, but these types of detectors have met with limited success.
What is needed then is an infrared detector which includes a method of separating the current caused by incident gamma radiation for use in a high radiation environment. It is therefore an object of the present invention to provide such an infrared detector.